Process for foaming aqueous protein-containing blasting agents

ABSTRACT

Passing a thickened protein-containing water-bearing blasting agent through a plurality of orifices at a pressure of about 40 to 160 psi to create a vacuum in the area where the blasting agent exits from the orifice, incorporating air or other gas in the blasting agent and, thereafter, reducing the velocity of the blasting agent to provide a foamed product.

United States atet Adams et al.

[151 3,678,140 51 July 18,1972

[54] PROCESS FOR FOAMING AQUEOUS PROTEIN-CONTAININ G BLASTING AGENTS Inventors: Philip E. Adam, Falling Waters, W. Va.;

Philip W. Fear-now, Hagerstown, Md.

Assignee: E. I. du Pont de Nemours and Company,

Wilmington, Del.

Filed: Dec. 3, 1969 Appl. No.: 881,771

US. Cl ..l49/l09, l49/2, 149/44,

149/60, 264/3 Int. Cl. C06b 21/02 Field of Search 149/2, 44, 60, l09; 264/3 References Cited UNITED STATES PATENTS 3,400,026 9/ i 968 Feamow 149/44 X Primary Examiner-Carl D. Quarforth Assistant Examinerestephen J. Lechert, Jr. Attorney-James J. Flynn [57] ABSTRACT Passing a thickened protein-containing water-bearing blasting agent through a plurality of orifices at a pressure of about 40 to 160 psi to create a vacuum in the area where the blasting agent exits from the orifice, incorporating air or other gas in the blasting agent and, thereafter, reducing the velocity of the blasting agent to provide a foamed product.

6CIalns,4Drawingl1gures Patented July 18, 1972 INVENTORS ADAMS PHILIP E PHILIP W. FEARNQW 21 /L: W Y

ATTORNEY PROCESS FOR FOAMING AQUEOUS PROTEIN- CONTAINING BLASTING AGENTS BACKGROUND OF THE INVENTION The advent of explosive compositions comprising an aqueous solution of an inorganic oxidizing salt, at least partly dissolved in water, together with one or more fuels and a gelling agent provided blasting operations with a variety of new explosive compositions having many desirable advantages, such as a wide variety of explosive properties, and better safety characteristics and economy, in both manufacture and use. In addition, proposed aqueous explosive compositions free of self-explosives, e.g., TNT, or metallic fuels, e.g., aluminum, offer added safety features and low cost. However, despite their inherent advantages, water-bearing explosive compositions have certain disadvantages with regard to their physical and explosive properties, particularly at low temperatures, e.g., 32 to 40F to 5C). After standing for a period of time, often as short a time as a few hours, whether in storage or in boreholes before detonation, water-bearing explosives, or water gels, tend to separate or settle into layers or to harden or solidify, instead of remaining soft and pliable. Accordingly, there is a definite need for blasting agents that will provide stable, soft aqueous explosive compositions capable of reliable detonations even at low temperatures and in small diameter holes, e.g., about 2 to inches.

Water-bearing explosives containing balanced quantities of fuels, oxidizing agents, and thickeners or stabilizers, but excluding high explosive or metallic sensitizers, require the occlusion of gases to lower the density of the composition and thus obtain the desired sensitivity and velocity of detonation. The successful occlusion of gas in explosive compositions is reflected in the density of the product. Densities of 1.00 to 1.25 glcc are generally desired. Inclusion of proteinaceous material, such as disclosed in U.S. Pat. No. 3,400,026, helps to create satisfactory gas-liquid emulsions. Gas occlusion may be provided by simple mechanical agitation or whipping, by gas injection, by chemical blowing agents, or by reactions that produce gaseous products such as nitrogen or carbon dioxide.

Although gas or air bubbles have been occluded in explosive compositions at the time of manufacture to produce a foamed product having the desired detonation properties, generally the effects are not long-lasting. Frequently, the foamed compositions are unstable, the entrapped air or gas is lost in a few hours or days, the foam collapses, and the density of the composition increases to an extent that reliability of detonation is impaired. Since it is common practice in some kinds of mining to load explosives into boreholes and let them remains for several weeks before blasting, there is obvious need for stable, reliable explosives that will retain their detonating properties under such conditions The present invention provides a means for manufacturing stable, permanent foamed explosive compositions that keep their foamed structure, retain their low density, and maintain their reliability of detonation during long periods in storage or in boreholes.

SUMMARY OF THE INVENTION The present invention provides a process for foaming blasting agents which comprises (a) passing a thickened proteincontaining water-bearing blasting agent through a plurality of orifices at a pressure of about 40 to 160, preferably 125 to 140, pounds per square inch into a suction chamber in order to form a plurality of streams of thickened explosive and create a vacuum in the area where the blasting agent exits therefrom; (b) simultaneously incorporating gas into the thickened explosive in the suction chamber so as to cause an intimate admixture of the gas with the thickened explosive; (c) thereafter reducing the velocity of the thickened explosive by subsequently passing it through an enlarged opening, and recovering the resulting foamed, thickened blasting agent. Accordingly, the thickened protein-containing water-bearing explosive slurry is foamed by forcing it to flow at high velocity through a converging nozzle into a suction chamber where air or other gas is entrained in the liquid by friction and other forces induced by the kinetic energy of the turbulent, highvelocity stream, and thence into a Venturi-shaped diffuser, i.e., a length of conduit of progressively increasing diameter, where the velocity is progressively reduced. Devices in which such a process may be carried out are known by the names ejector, injector, siphon, water jet, eductor, jet pump, exhauster, etc.

It has been found that by pumping the thickened proteincontaining water bearing explosive slurry through an eductor or jet ejector under the conditions specified, a stable foamed explosive of low density is produced that retains its characteristics and allows the explosive to be stored for long periods of time in a stable condition without losing any of its reliability of detonation.

A pump having a rubber impeller is a preferred means of propelling the slurry through the foaming device, e.g., eductor having a multiple nozzle design. Alternatively, the slurry may be forced through the nozzle by gas pressure, which also offers the opportunity of incorporating more gas in the product.

The water-bearing blasting agents contain an inorganic oxidizing salt, fuel, thickener, proteinaceous material and gas bubbles. The proteinaceous material in the water-bearing explosive is any protein or protein derivative, such as those obtained by hydrolysis, amidation, acylation or other chemical reaction applied to a protein that is soluble in the explosive composition. By soluble is meant that at least about 10 percent by weight of the proteinaceous material in the waterbearing explosive composition having a pH of 3 to 10 dissolves therein, the balance of the proteinaceous material being either water-soluble or water-dispersible. Representative proteinaceous materials that are present in the water-bearing explosive composition include simple proteins, that is proteins that yield, on complete hydrolysis, chiefly a-amino acids; conjugated proteins, that is, compounds of a protein with some other molecule or molecules referred to as a prosthetic group; and protein derivatives, that is, products formed by the action of heat or other physical forces, or by hydrolytic agents, such as denatured proteins or peptides. The presence of proteinaceous material in the blasting agent promotes the occlusion of the fine gas bubbles that sensitize the blasting agent. The product, which is pumped through a flexible hose into a borehole, will retain its useful explosive properties for long periods, without segregation, even when the explosive remains in the borehole for many days before being detonated. The compositions also show a surprising resistance to the latching effects frequently encountered in wet boreholes. The amount of proteinaceous material in the blasting agent to be formed can be varied within a rather wide range, generally it contains about 0.01 percent to 10 percent, usually 0.] to 3 percent, by weight, proteinaceous material. Details of typical compositions that may be foamed in the process of this invention are given in U.S. Pat. No. 3,400,026 and such disclosure is incorporated herein by reference. Other protein-containing explosive compositions that are particularly effective blasting agents, and that may be foamed by the process of this invention, are described in copending application Ser. No. 815,487, filed Apr. 11, 1969 and assigned to the assignee of the present application and such disclosure is incorporated herein by reference.

The blasting agents of this invention generally contain 5 to 20 percent water and are thickened by incorporating any of the conventional thickeners used in water-bearing explosive compositions. thickened as used herein refers to compositions in which the viscosity of the aqueous phase has been materially increased, e.g., to 20,000 cps. or more, as well as gelled products including those gels which are crosslinked. Representative thickening agents, used in amounts ranging from, by weight of the compositions, 0.1 to 10 percent, preferably from 0.2 to 5 percent, and most preferably 0.2 to 2 percent, include gum arabic; seaweed colloids such as agaragar; seed extracts such as locust bean; starches and modified starches such as dextrins and hydroxyethyl starch; waterdispersible derivatives of cellulose such as methyl cellulose and sodium carboxymethyl cellulose and high molecular weight polyethylene oxides as well as mixtures of two or more of the above thickening agents. Of these, guar gum is preferred.

Any gas that is inert toward the thickened protein-containing water-bearing explosive composition can be incorporated therein. The gas can be introduced in the product stream by injection or, preferably, by means of an aperture in the product stream line, such as a suction leg, which serves to draw gas into the system. Such gases that can be used in the process include nitrogen, carbon dioxide, hydrogen, oxygen, or air. The gas can be incorporated in the blasting agent by the application of pressure on the gas. However, preferably, atmospheric gas, is used as the foaming agent and it is drawn into the suction leg for incorporation in the blasting agent without the application of pressure due to the creation of a vacuum in the area where the blasting agent exits from the orifices.

The velocity of the blasting agent issuing out of the orifices of, for example, an eductor, is reduced in order to further enhance the mixture of blasting agent and gas, e.g. air. The velocity of the stream can be conveniently reduced by merely passing it through an enlarged opening, for example, through a diffuser of the Venturi type.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 in the drawing illustrates schematically one apparatus arrangement for carrying out the process of this invention;

FIG. 2 is an enlarged cross-sectional view of the eductor showing the nozzle;

FIG. 3 is an enlarged fragmentary sectional view of the nozzle of the eductor; and

FIG. 4 is an end view of the nozzle shown in FIG. 3 showing the location of the orifices.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more fully describe the present invention, reference is made to the accompanying drawing wherein protein-containing water-bearing explosive is formulated in mixing tank 1 provided with stirrer 2. The explosive composition is circulated by means of pump 5 from mixing tank 1 through a flow-regulative valve 3 and flexible hose 4 at an operating pressure indicated by pressure gauge 6. The explosive continues to flow through hose 4 and into eductor 7 where it is forced through inlet 9 and orifices 12 in nozzle 10 of the eductor at pressures of from about 40 to 160 psi to form a stream of explosive. Gas, e.g., atmospheric air, is drawn in through suction leg 11 due to the suction created by the explosive issuing out of the orifices under pressure and the gas is incorporated in the turbulent explosive in suction chamber 13. Subsequently, the velocity of the explosive composition is reduced by passing it through diffuser 14. The foamed explosive is collected in receiver 8. Preferably, the orifices 12 in nozzle 10 may be drilled at an angle 15 with the center line of the nozzle to insure turbulent impingement of the slurry streams, as shown in FIG. 3. Different nozzles having two or more orifices may be used to vary the eductor capacity and to better control the density of the product.

The water-bearing agents contain, in addition to the proteinaceous material and thickener, an inorganic oxidizing salt and fuel. The inorganic oxidizing salt usually comprises at least about percent by weight of the total composition and it can be any of the soluble salts conventionally used in waterbearing explosive compositions such as alkali metal, alkaline earth metal, and ammonium nitrates, chromates, dichromates, chlorates, and perchlorates, as well as mixtures of two or more such salts. Preferably, the inorganic oxidizing salt component contains ammonium nitrate, either alone or in combination with sodium nitrate. Preferably, the composition contains about 20 to 70 percent ammonium nitrate and 5 to 25 percent sodium nitrate by weight based on the weight of the total composition. Generally, the explosive contains a fuel. Representative fuels include certain nitro aromatic hydrocarbons suchas monoand dinitrobenzenes and monoand dinitrotoluenes; sulfurous fuels including sulfur; and carbonaceous fuels such as finely divided coal, wood, or sugar. In general, the explosive composition contains up to about 25 percent and preferably from 2 to 20 percent, by weight fuel.

As mentioned above, proteinaceous materials that are soluble to the extent indicated in the water-bearing explosive are used. Representative simple proteins include albumins such as ovalbumin and lactalbumin occurring, respectively, in egg white and milk, globulins such as ovoglobulin and lactoglobulin and conjugated proteins such as the glycoprotein mucin. Protein derivatives used in the explosive composition include partially hydrolyzed milk protein and extracted collagen derivatives. Of these, egg albumin is especially preferred because of its high solubility and its exceptional ability in producing and maintaining a foamed structure.

The water-bearing composition can also contain conventional crosslinking agents that thicken the explosive such as potassium antimony tartrate, chromium salts, acrylamides, and the like.

In the examples that follow, the general procedure used was to charge the ingredients into the mixing tank, stir them until thoroughly mixed, force the mixture under high pressure through the eductor, and collect the foamed product. Variations in this procedure are described in the individual examples.

EXAMPLE 1 A water-bearing blasting agent was prepared by mixing the following ingredients:

Ammonium nitrate 48.5% Sodium nitrate l5.0 Monomethylamine nitrate l2.0 Water l5.7 Sugar 2.0 Sulfur, fine 3.0 Coal, fine 3.0 Jaguar 180 (guar gum) 0.8

100.0% Glycol 1.5 lbs/cwt Egg albumin 0.2 lbs/cwt The mixture was pumped by a Waukesha pump having rubber lobes through an eductor, equipped with a nozzle having six three-sixteenth inch diameter orifices, at a pump discharge pressure of 50 psi. The blasting agent flowing through the orifices exited into a suction chamber to which atmospheric air was supplied through a vacuum leg for incorporation in the explosive. The velocity of the blasting agent was reduced by passing it through an enlarged opening, i.e. a diffuser. After two passes through the eductor system, the density of the product had changed from a density of 1.42 to 1.25 g/cc. Samples of this material were detonated at 1 16F by one No. 8 cap. Other samples of the foamed product were retained in storage and after six months had not increased in density or showed other evidence of change and they were detonated with a primer.

EXAMPLE 2 The procedure described in Example 1 was repeated except the blasting agent was pumped at psi through an eductor having three three-sixteenth inch diameter holes in the nozzle. One pass through the eductor resulted in the explosive having a density of 1.10 g/cc at a pumping rate of 20 gal/min.

EXAMPLE 3 The procedure described in Example 1 was repeated except the blasting agent was pumped at psi through an eductor with three five-sixteenth inch diameter orifices in the nozzle. One pass of the product through the system resulted in the blasting agent having a density of 1.12 g/cc at a pumping rate of 103 gal/min. of the foamed product.

' EXAMPLE 4 To demonstrate on-site production of a water-bearing explosive foamed by passage through an eductor for a full scale commercial blast, a 15,000 pound mix of the composition shown in Example 1 was manufactured by the following steps:

1. A slurry was made of the ammonium nitrate, sodium nitrate, water, monomethylamine nitrate, sugar, coal, sulfur and egg albumin in the mix tank.

2. To the slurry was added 45 percent of a guar-glycol solution containing 135 lbs. Jaguar 180 (guar gum) and 240 lbs. of ethylene glycol.

. The slurry was pumped by a Waukesha pump at 100-125 psi through an eductor having three three-sixteenth inch diameter orifices in the nozzle and recirculated until the density of the total mix ranged between 1.05 and 1.08 g/cc, while at 130F; then the remaining guar glycol solution was added before the explosive slurry was pumped to its destination. The product was stored for 3 months and samples after storage showed no increase in density or evidence of other change. Samples after storage were detonated with a primer in air at 40F in 6 inch diameters at 4,500 m/sec.

EXAMPLE 5 The procedure described above in Example 1 was repeated except nitrogen gas was forced under pressure through the suction leg of the eductor into the suction chamber. The density of the slurry explosive was lowered from 1.43 to 1.21 g/cc. Samples of the product were stored and after 6 months had not increased in density or showed other evidence of change. Samples after storage were detonated with a primer.

We claim:

1. A process for foaming blasting agents which comprises:

a. passing a thickened proteinaceous-containing water bearing blasting agent through a plurality of orifices at a pressure of about 40 to 160 pounds per square inch into a suction chamber in order to form a plurality of streams of thickened explosive and create a vacuum in the area where the blasting agent exits therefrom;

b. simultaneously incorporating gas into the thickened explosive in the suction chamber after it exits from the orifices so as to cause an intimate admixture of the gas with the thickened explosive;

c. thereafter reducing the velocity of the thickened explosive by subsequently passing it through an enlarged opening, and recovering the resulting foamed, thickened blasting agent.

2. A process of claim 1 where the gas is air.

3. A process of claim 2 wherein the water-bearing explosive contains an inorganic oxidizing salt and egg albumin.

4. A process of claim 3 wherein the pressure is from about to pounds per square inch.

5. A process of claim 3 wherein the water-bearing explosive contains from about 0.1 to 10 percent thickening agent.

6. A process of claim 5 wherein the thickening agent is guar 

2. A process of claim 1 where the gas is air.
 3. A process of claim 2 wherein the water-bearing explosive contains an inorganic oxidizing salt and egg albumin.
 4. A process of claim 3 whereiN the pressure is from about 125 to 140 pounds per square inch.
 5. A process of claim 3 wherein the water-bearing explosive contains from about 0.1 to 10 percent thickening agent.
 6. A process of claim 5 wherein the thickening agent is guar gum. 